This invention relates generally to water vessels, and more particularly to a single hulled sailboat designed to have a pair of outwardly extending and retractable horizontal hydrofoil members which eliminate the need for centerline ballast or keel commonly found in most sailboats.
At the present time, the only effective method of off-setting the heeling moment caused by wind pressure on the sails and mast of a mono-hull sailboat is by placing weight in the form of a lead ballast as low as possible in a keel. Most sailboats use between thirty-five to forty percent of displacement/weight of the sailboat for ballast. For example, a 20,000 lbs sailboat normally carries about 7,500 lbs of fixed weight for ballast. The sail plan of the sailboat must be designed to be large enough to move the construction weight of the sailboat, the weight of any machinery and tanks mounted therein, the weight of people and gear, and the weight of the fixed ballast.
Water has also been used to reduce the amount of lead or iron ballast by placing tanks on each side of the sailboat's hull and pumping water from one tank to the other so as to increase the vessel's stability. One disadvantage associated with this arrangement is that the water ballast tank placement and size is limited by the shape and size of the vessel. Since the tanks are relatively close to the centerline, the amount of water in pounds (62.4 lbs per cubic feet for fresh water) must approximate the weight of the fixed ballast removed. This is difficult to achieve with water since a cubic foot of lead weighs approximately 700 lbs and a cubic foot of water is less than ten times that weight, i.e., 62.4 lbs. Thus, in order to substitute water for lead, a large amount of space within the hull of the sailboat must be dedicated for the large tanks which would be required to house the water.
Another issue confronting sailboat designers is draft which is defined as the vertical depth of the hull below the water line. Draft reduction has been achieved for centuries with the use of movable and/or swingable centerboards, dagger boards, and lee boards. However, when any of these types of boards are raised for shallow water sailing, the sailboats do not sail well. For example, with a catboat hull having less than eighteen inches of draft, it is nearly impossible to control under sail with the board raised due to leeward movement, i.e., the hull sliding sideways from the wind pressure on the sail. Most centerboard mono-hulls without keel surface cannot be sailed effectively with the centerboard raised. Thus, the advantage of having shallow water draft is negated since the board must be lowered to control the sailboat.
Multi-hull designs address some of the sailing draft issues. The two multi-hull type sailboats commonly found on the market are the catamaran and the trimaran. The catamaran utilizes two equal sized hulls joined together by a beam structure. The trimaran incorporates a narrow main hull with two smaller pontoons placed on either side of the main hull. Both multi-hull designs use width/beam to obtain stability and to offset the pressure caused by the sails. Multi-hulls do not use fixed ballast, and the hull shapes are extremely shallow and narrow as compared to mono-hull vessels. However, they still require a centerboard or dagger board for sailing performance to control leeward movement.
One problem associated with multi-hull sailboats is the extreme beam which precludes the vessel from docking in conventionally spaced slips found in marinas. Even in crowded mooring and anchorage areas, multi-hull vessels can present problems due to their width. For example, a common thirty-two foot catamaran typically has over an eighteen foot beam whereas a mono-hull of the same length has a ten or an eleven foot beam. Some trimarans are designed with a folding or swing mechanism which moves the two outboard hulls closer to the main hull for docking and trailering. However, with this design, the main hull is very narrow and requires a dagger board. Another disadvantage of multi-hull designs is that they are difficult to self-right after capsizing. In the extreme situation where wind or seas capsize a multi-hull, the same factors that allow them to sail without ballast (e.g., excessive beam), prevent them from returning upright.
The present invention is directed to a horizontal hydrofoil member for a mono-hull sailboat of the type having a mono-hull with no fixed ballast comprising an elongate arm portion adapted to extend laterally outwardly away from the sailboat along a generally horizontal plane when in use. The arm portion has an upwardly-facing surface, a downwardly-facing surface, and an outer end portion which flares upwardly relative to the horizontal plane. The hydrofoil member further comprises a pontoon element mounted on the downwardly-facing surface of the arm portion at the outer end portion. The pontoon element is adapted to engage and displace water when in use and has low drag and high lift capabilities for stabilizing the sailboat.
More specifically, the pontoon element is of hollow construction for selectively storing fluid therein. The pontoon element, when filled with fluid, provides a ballast force against the sailboat for stabilizing the same. Means for supplying fluid to the pontoon element from the sailboat comprises a pump housed within the sailboat and a hose extending between the pump and the hollow pontoon element. The pump is in fluid communication with a reservoir of fluid for pumping fluid into and out of the hollow pontoon element.
The hydrofoil member further comprises means for pivotally and hingedly mounting the arm portion of the hydrofoil member on the sailboat. The mounting means comprises a plate pivotally mounted by a pin to the sailboat wherein the arm portion is hingedly attached to the plate. The arrangement is such that the arm portion and pontoon element are movable between a stowed position in which they extend along a side of the sailboat and a use position in which the arm portion via the leg portion is pivoted to extend vertically and then hingedly lowered so as to achieve its generally horizontal position. The mounting means further comprises a support bracket mounted on the sailboat wherein the plate is pivotally mounted by the pin to the support bracket. A thrust arm controls the elevation of the hydrofoil member with respect to the horizontal plane. The thrust arm is pivotally attached at an outer end to the arm portion of the hydrofoil member and threadably attached at its other opposite end to the support bracket. The support bracket is mounted on the deck of the boat to an adjustable flat track. The arrangement is such that the plate, arm portion and support bracket can be moved along the track so as to adjust the location of the hydrofoil member with respect to the sailboat.
Accordingly, among the several objects of the present invention are the provision of a hydrofoil member mounted on a hull of sailboat which enables the sailboat to be designed without fixed ballast weight or a centerboard, thereby decreasing the weight of the sailboat for making it faster, and decreasing the draft of the sailboat for enabling it to travel in shallow waters; the provision of such a hydrofoil member which is capable of being selectively filled with fluid for stabilizing purposes; the provision of such a hydrofoil member which is pivotally and hingedly attached to the hull of the sailboat thereby enabling the operator of the sailboat to move the hydrofoil member to a stowed position when docking or transporting the sailboat; the provision of such a hydrofoil member which is especially designed for stabilizing the sailboat; the provision of such a hydrofoil member which is lightweight; the provision of such a hydrofoil member which is adjustable to provide for angle of lift attack and foil dihedral to adjust drag component; and the provision of such a hydrofoil member which is relatively simple to operate and which moves easily to a use position.
Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.